<TABLE> <S> <C>

<ARTICLE> 6
<LEGEND>
This schedule contains Summary Financial Information extracted from the Form
N-SAR and the financial statements and is qualified in its entirety by
references to such documents.
</LEGEND>
<SERIES>
   <NUMBER> 022
   <NAME> NUVEEN NATIONAL INSURED MUNICIPAL BOND FUND - CLASS B
<MULTIPLIER> 1000

<S>                             <C>
<PERIOD-TYPE>                   12-MOS
<FISCAL-YEAR-END>                          APR-30-2000
<PERIOD-START>                             MAY-01-1999
<PERIOD-END>                               APR-30-2000
<INVESTMENTS-AT-COST>                           748495
<INVESTMENTS-AT-VALUE>                          772320
<RECEIVABLES>                                    19582
<ASSETS-OTHER>                                    2235
<OTHER-ITEMS-ASSETS>                                 0
<TOTAL-ASSETS>                                  794137
<PAYABLE-FOR-SECURITIES>                         15851
<SENIOR-LONG-TERM-DEBT>                              0
<OTHER-ITEMS-LIABILITIES>                         3660
<TOTAL-LIABILITIES>                              19511
<SENIOR-EQUITY>                                      0
<PAID-IN-CAPITAL-COMMON>                        764178
<SHARES-COMMON-STOCK>                             1646
<SHARES-COMMON-PRIOR>                             1219
<ACCUMULATED-NII-CURRENT>                          360
<OVERDISTRIBUTION-NII>                               0
<ACCUMULATED-NET-GAINS>                        (13737)
<OVERDISTRIBUTION-GAINS>                             0
<ACCUM-APPREC-OR-DEPREC>                         23825
<NET-ASSETS>                                    774626
<DIVIDEND-INCOME>                                    0
<INTEREST-INCOME>                                48032
<OTHER-INCOME>                                       0
<EXPENSES-NET>                                    5531
<NET-INVESTMENT-INCOME>                          42501
<REALIZED-GAINS-CURRENT>                       (13653)
<APPREC-INCREASE-CURRENT>                      (47069)
<NET-CHANGE-FROM-OPS>                          (18221)
<EQUALIZATION>                                       0
<DISTRIBUTIONS-OF-INCOME>                          683
<DISTRIBUTIONS-OF-GAINS>                            32
<DISTRIBUTIONS-OTHER>                                0
<NUMBER-OF-SHARES-SOLD>                            732
<NUMBER-OF-SHARES-REDEEMED>                        335
<SHARES-REINVESTED>                                 31
<NET-CHANGE-IN-ASSETS>                         (86136)
<ACCUMULATED-NII-PRIOR>                            567
<ACCUMULATED-GAINS-PRIOR>                         1499
<OVERDISTRIB-NII-PRIOR>                              0
<OVERDIST-NET-GAINS-PRIOR>                           0
<GROSS-ADVISORY-FEES>                             3866
<INTEREST-EXPENSE>                                   0
<GROSS-EXPENSE>                                   5596
<AVERAGE-NET-ASSETS>                             15686
<PER-SHARE-NAV-BEGIN>                            11.16
<PER-SHARE-NII>                                    .46
<PER-SHARE-GAIN-APPREC>                          (.79)
<PER-SHARE-DIVIDEND>                             (.46)
<PER-SHARE-DISTRIBUTIONS>                        (.02)
<RETURNS-OF-CAPITAL>                                 0
<PER-SHARE-NAV-END>                              10.35
<EXPENSE-RATIO>                                   1.58


</TABLE>